The present invention relates to integrated circuit devices and, more particularly, to integrated circuit devices, such as memory devices, including a ferroelectric capacitor and methods for manufacturing the same.
Recently, ferroelectric memory devices using ferroelectric layers have been considered as an alternative approach for certain memory applications. Ferroelectric memory devices are generally divided into two categories. The first category includes devices using a ferroelectric capacitor as described, for example, in U.S. Pat. No. 5,523,964. The second category includes devices having a ferroelectric field emission transistor (FET) as described, for example, in U.S. Pat. No. 5,198,994. These devices may provide higher-speed read and write operations and/or lower power consumption than other types of memory devices. For example, these device may have non-volatile memory properties comparable to that of the flash memory, and an operation speed, a low power operation, a low voltage operation, and reliability comparable to those of static random access memory (SRAM) and the like.
Ferroelectric memory devices may be used for non-volatile memory by using their ferroelectric characteristics to retain data when no power is supplied to the device. This non-volatile property of the ferroelectric memory device is based on an inherent property of the ferroelectric material used in the device. The ferroelectric material generally has two stable remnant polarization (Pr) states. The remnant polarization states may be changed by application of an external electric field and the new state is maintained after the external electric field is removed.
Much like the structure of a typically dynamic random access memory (DRAM) capacitor, a ferroelectric capacitor may be used to store data in a memory cell. The ferroelectric capacitor includes a ferroelectric material between the two electrodes. While the DRAM capacitor generally stores data by charging of a capacitor including a dielectric film interposed between two electrodes, the ferroelectric capacitor generally stores data using the remnant polarization of the ferroelectric material interposed between two electrodes.
As the ferroelectric capacitor employs a ferroelectric material rather than a dielectric material, the fabrication process for the ferroelectric capacitor differs from that for a DRAM memory device. For example, because the polysilicon electrode material generally used in a DRAM memory device actively reacts with the ferroelectric material used in a ferroelectric capacitor, a different material may be used for the electrodes. A noble metal, such as platinum (Pt), or a conductive oxide, such as iridium dioxide (IrO2)s, may be used in place of polysilicon as the electrode material of the ferroelectric capacitor.
In a typical ferroelectric capacitor fabrication process, a lower electrode material, a ferroelectric film and an upper electrode material are sequentially deposited on an integrated circuit (semiconductor) substrate and etched to have a predetermined pattern. As an electrode material, such as platinum, is generally not etched to an optimal shape, the resulting ferroelectric capacitor generally has a tilted sidewall profile. In other words, the ferroelectric capacitor has a profile with wider sidewalls in the lower portion than in the upper portion of the capacitor. Such a profile may cause adjacent ferroelectric capacitors to be, undesirably, electrically connected with each other. If the adjacent capacitors are placed farther apart to avoid this problem, the integration density of the integrated circuit device may be reduced. Also, the effective contact area between the ferroelectric film and the electrode may be reduced as a result of the tilted sidewall profile of the ferroelectric capacitor. Furthermore, as the ferroelectric film may be subjected to etch damage during the etching process of the lower electrode, the ferroelectricity of the ferroeletric film may be deteriorated.